Method and apparatus for determining an etch property using an endpoint signal

ABSTRACT

The present invention presents a plasma processing system for etching a layer on a substrate comprising a process chamber, a diagnostic system coupled to the process chamber and configured to measure at least one endpoint signal, and a controller coupled to the diagnostic system and configured to determine in-situ at least one of an etch rate and an etch rate uniformity of the etching from the endpoint signal. Furthermore, an in-situ method of determining an etch property for etching a layer on a substrate in a plasma processing system is presented comprising the steps: providing a thickness of the layer; etching the layer on the substrate; measuring at least one endpoint signal using a diagnostic system coupled to the plasma processing system, wherein the endpoint signal comprises an endpoint transition; and determining the etch rate from a ratio of the thickness to a difference between a time during the endpoint transition and a starting time of the etching.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/422,511, filed Oct. 31, 2002, and is related to co-pendingapplication 60/422,510, entitled “Method and apparatus for detectingendpoint,” Attorney docket No. 228160USUS6YA PROV, filed on Oct. 31,2002. The contents of these applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for plasmaprocessing a substrate, and more particularly to an in-situ method andapparatus for determining an etch property of a layer on a substrateduring a plasma etch process.

2. Discussion of the Background

The fabrication of integrated circuits (IC) in the semiconductor devicemanufacturing industry typically employs plasma to create and assistsurface chemistry necessary to remove material from and to depositmaterial to a substrate. In general, plasma is formed within a plasmaprocessing system under vacuum conditions by heating electrons toenergies sufficient to sustain ionizing collisions with a suppliedprocess gas. Moreover, the heated electrons can have energy sufficientto sustain dissociative collisions and, therefore, a specific set ofgases under predetermined conditions (e.g., chamber pressure, gas flowrate, etc.) are chosen to produce a population of charged species andchemically reactive species suitable to the particular process beingperformed within the processing system (e.g., etching processes duringwhich materials are removed from the substrate or deposition processesduring which materials are added to the substrate). During, for example,an etch process, monitoring the etch rate and the spatial uniformity ofthe etch rate can be very important when determining the state of aplasma processing system and for qualifying such a system following amaintenance interval. In current manufacturing practice, systemqualification is usually performed by executing a series ofqualification substrates and measuring the resultant etch rate and etchrate uniformity to determine whether to continue production or toperform system maintenance such as a wet clean of the process chamber.Furthermore, the method of determining the etch rate and the uniformityof the etch rate involves substrate cleaving (i.e. sacrifice of thesubstrate), and SEM (scanning electron microscope) analysis. Using SEMmicrographs, feature etch depths can be measured at different locationson the qualification substrates and, when combined with the etch time,information for etch rate and etch rate uniformity can be acquired.

Consequently, significant system production time is expended andqualification substrates are consumed, hence, leading to greaterproduction costs during the tedious qualification process. Moreover,production substrates and qualification substrates can differsubstantially and, therefore, lead to erroneous conclusions regardingsystem qualification. For example, the measured etch rate onqualification substrates does not necessarily reflect the real etch rateon the production wafer.

SUMMARY OF THE INVENTION

The present invention provides a method and system for determining anetch property during an etch process, wherein the method advantageouslyaddresses the above-identified shortcomings.

It is an object of the present invention to provide a plasma processingsystem for etching a layer on a substrate comprising: a process chamber;a diagnostic system coupled to the process chamber and configured tomeasure at least one endpoint signal; and a controller coupled to thediagnostic system and configured to determine in-situ at least one of anetch rate and an etch rate uniformity of the etching from the endpointsignal and a thickness of the layer, wherein the thickness comprises atleast one of a minimum thickness, a maximum thickness, a mean thickness,and a thickness range.

It is another object of the present invention to provide an in-situmethod of determining an etch property for etching a layer on asubstrate in a plasma processing system comprising: providing athickness of the layer, wherein the thickness comprises at least one ofa minimum thickness, a maximum thickness, a mean thickness, and athickness range; etching the layer on the substrate; measuring at leastone endpoint signal using a diagnostic system coupled to the plasmaprocessing system, wherein the endpoint signal comprises an endpointtransition; and determining the etch rate from a ratio of the thicknessto a difference between a time during the endpoint transition and astarting time of the etching.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the invention will become more apparentand more readily appreciated from the following detailed description ofthe exemplary embodiments of the invention taken in conjunction with theaccompanying drawings, where:

FIG. 1 shows a simplified block diagram of a plasma processing systemaccording to an embodiment of the present invention;

FIG. 2 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 3 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 4 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 5 shows a schematic diagram of a plasma processing system accordingto another embodiment of the present invention;

FIG. 6 illustrates an exemplary endpoint signal according to anembodiment of the present invention;

FIGS. 7A-7D illustrate a series of graphs showing various exemplaryendpoint signals according to another embodiment of the presentinvention;

FIGS. 8A-8B illustrate an exemplary raw and filtered endpoint signalaccording to another embodiment of the present invention; and

FIG. 9 presents an in-situ method of determining an etch property foretching a layer on a substrate in a plasma processing system accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

According to an embodiment of the present invention, a plasma processingsystem 1 is depicted in FIG. 1 comprising a plasma processing chamber10, a diagnostic system 12 coupled to the process chamber 10, and acontroller 14 coupled to the diagnostic system 12. The controller 14 isconfigured to receive at least one endpoint signal from the diagnosticsystem 12 and to determine an etch property, such as an etch rate or anetch rate uniformity, from the at least one endpoint signal. In theembodiment illustrated in FIG. 1, plasma processing system 1 utilizes aplasma for material processing. Desirably, plasma processing system 1comprises an etch chamber.

According to the illustrated embodiment of the present inventiondepicted in FIG. 2, plasma processing system 1 can comprise plasmaprocessing chamber 10, substrate holder 20, upon which a substrate 25(e.g., a semiconductor wafer or a liquid crystal display panel) to beprocessed is affixed, and vacuum pumping system 30. Substrate 25 can be,for example, a semiconductor substrate, a wafer or a liquid crystaldisplay. Plasma processing chamber 10 can be, for example, configured tofacilitate the generation of plasma in processing region 15 adjacent asurface of substrate 25. An ionizable gas or mixture of gases isintroduced via gas injection system (not shown) and the process pressureis adjusted. For example, a control mechanism (not shown) can be used tothrottle the vacuum pumping system 30. Desirably, plasma is utilized tocreate materials specific to a pre-determined materials process, and toaid the removal of material from the exposed surfaces of substrate 25.The plasma processing system 1 can be configured to process 200 mmsubstrates, 300 mm substrates, or larger.

Substrate 25 can be, for example, transferred into and out of plasmaprocessing chamber 10 through a slot valve (not shown) and chamberfeed-through (not shown) via robotic substrate transfer system where itis received by substrate lift pins (not shown) housed within substrateholder 20 and mechanically translated by devices housed therein. Oncesubstrate 25 is received from substrate transfer system, it is loweredto an upper surface of substrate holder 20.

Substrate 25 can be, for example, affixed to the substrate holder 20 viaan electrostatic clamping system. Furthermore, substrate holder 20 can,for example, further include a cooling system including a re-circulatingcoolant flow that receives heat from substrate holder 20 and transfersheat to a heat exchanger system (not shown), or when heating, transfersheat from the heat exchanger system. Moreover, gas can, for example, bedelivered to the back-side of substrate 25 via a backside gas system toimprove the gas-gap thermal conductance between substrate 25 andsubstrate holder 20. Such a system can be utilized when temperaturecontrol of the substrate is required at elevated or reducedtemperatures. In other embodiments, heating elements, such as resistiveheating elements, or thermoelectric heaters/coolers can be included.

Plasma processing chamber 10 can, for example, further comprise avertical translational device (not shown) surrounded by a bellows (notshown) coupled to the substrate holder 20 and the plasma processingchamber 10, and configured to seal the vertical translational devicefrom the reduced pressure atmosphere in plasma processing chamber 10.Additionally, a bellows shield (not shown) can, for example, be coupledto the substrate holder 20 and configured to protect the bellows fromthe processing plasma. Substrate holder 20 can, for example, furtherprovide a focus ring (not shown), a shield ring (not shown), and abaffle plate (not shown).

In the illustrated embodiment, shown in FIG. 2, substrate holder 20 cancomprise an electrode through which RF power is coupled to theprocessing plasma in process space 15. For example, substrate holder 20can be electrically biased at a RF voltage via the transmission of RFpower from a RF generator 40 through an impedance match network 50 tosubstrate holder 20. The RF bias can serve to heat electrons to form andmaintain plasma. In this configuration, the system can operate as areactive ion etch (RIE) reactor, wherein the chamber and upper gasinjection electrode serve as ground surfaces. A typical frequency forthe RF bias can range from 1 MHz to 100 MHz and is preferably 13.56 MHz.RF systems for plasma processing are well known to those skilled in theart.

Alternately, RF power is applied to the substrate holder electrode atmultiple frequencies. Furthermore, impedance match network 50 serves toincrease the transfer of RF power to plasma in plasma processing chamber10 by minimizing the reflected power. Match network topologies (e.g.L-type, π-type, T-type, etc.) and automatic control methods are wellknown to those skilled in the art.

With continuing reference to FIG. 2, process gas can be, for example,introduced to processing region 15 through gas injection system (notshown). Process gas can, for example, include a mixture of gases such asargon, CF4 and O2, or argon, C4F8 and O2 for oxide etch applications, orother chemistries such as O2/CO/Ar/C4F8, O2/CO/Ar/C5F8, O2/CO/Ar/C4F6,O2/Ar/C4F6, O2/Ar/C5F8, N2/H2, as well as other similar chemistriesknown in the art. The gas injection system can include a showerhead,where process gas is supplied from a gas delivery system (not shown) tothe processing region 15 through a gas injection plenum (not shown), aseries of baffle plates (not shown) and a multi-orifice showerhead gasinjection plate (not shown). Gas injection systems are well known tothose skilled in the art of vacuum processing.

Vacuum pump system 30 can, for example, include a turbo-molecular vacuumpump (TMP) capable of a pumping speed up to 5000 liters per second (andgreater) and a gate valve for throttling the chamber pressure. Inconventional plasma processing devices utilized for dry plasma etch, a1000 to 3000 liter per second TMP is generally employed. TMPs are usefulfor low pressure processing, typically less than 50 mTorr. At higherpressures, the TMP pumping speed falls off dramatically. For highpressure processing (i.e., greater than 100 mTorr), a mechanical boosterpump and dry roughing pump can be used. Furthermore, a device formonitoring chamber pressure (not shown) can be coupled to the plasmaprocessing chamber 10. The pressure measuring device can be, forexample, a Type 628B Baratron absolute capacitance manometercommercially available from MKS Instruments, Inc. (Andover, Mass.).

Controller 14 comprises a microprocessor, memory, and a digital I/O portcapable of generating control signals sufficient to communicate andactivate inputs to plasma processing system 1 as well as monitor outputsfrom plasma processing system 1. Moreover, controller 14 can be coupledto and can exchange information with RF generator 40, impedance matchnetwork 50, the gas injection system (not shown), vacuum pump system 30,as well as the backside gas delivery system (not shown), thesubstrate/substrate holder temperature measurement system (not shown),and the electrostatic clamping system (not shown). For example, aprogram stored in the memory can be utilized to activate the inputs tothe aforementioned components of plasma processing system 1 according toa stored process recipe. One example of controller 14 is a DELLPRECISION WORKSTATION 610™, available from Dell Corporation, Austin,Tex.

The diagnostic system 12 can include an optical diagnostic subsystem.The optical diagnostic subsystem can comprise a detector such as a(silicon) photodiode or a photomultiplier tube (PMT) for measuring thetotal light intensity emitted from the plasma. The diagnostic system 12can further include an optical filter such as a narrow-band interferencefilter. In an alternate embodiment, the diagnostic system 12 can includeat least one of a line CCD (charge coupled device), a CID (chargeinjection device) array, and a light dispersing device such as a gratingor a prism. Additionally, diagnostic system 12 can include amonochromator (e.g., grating/detector system) for measuring light at agiven wavelength, or a spectrometer (e.g., with a rotating grating) formeasuring the light spectrum such as, for example, the device describedin U.S. Pat. No. 5,888,337. Furthermore, diagnostic system 12 can alsocomprise a processor coupled to the optical diagnostic subsystem and tothe controller 14 for controlling the operation of the opticaldiagnostic system.

For example, diagnostic system 12 can include a high resolution OESsensor from Peak Sensor Systems, or Verity Instruments, Inc. Such an OESsensor has a broad spectrum that spans the ultraviolet (UV), visible(VIS) and near infrared (NIR) light spectrums. The resolution isapproximately 1.4 Angstroms, that is, the sensor is capable ofcollecting 5550 wavelengths from 240 to 1000 nm. The sensor is equippedwith high sensitivity miniature fiber optic UV-VIS-NIR spectrometerswhich are, in turn, integrated with 2048 pixel linear CCD arrays.

The spectrometers receive light transmitted through single and bundledoptical fibers, where the light output from the optical fibers isdispersed across the line CCD array using a fixed grating. Similar tothe configuration described above, light emitting through an opticalvacuum window is focused onto the input end of the optical fibers via aconvex spherical lens. Three spectrometers, each specifically tuned fora given spectral range (UV, VIS and NIR), form a sensor for a processchamber. Each spectrometer includes an independent A/D converter. Andlastly, depending upon the sensor utilization, a full emission spectrumcan be recorded every 0.1 to 1.0 seconds.

Alternately, diagnostic system 12 can comprise an electrical diagnosticsubsystem that can include at least one of a current and/or voltageprobe for monitoring an electrical property of the plasma processingsystem 1, a power meter, and a spectrum analyzer. For example, plasmaprocessing systems often employ RF power to form plasma, in which case,a RF transmission line, such as, for instance, a coaxial cable orstructure, is employed to couple RF energy to the plasma through anelectrical coupling element (i.e. inductive coil, electrode, etc.).Electrical measurements using, for example, a current-voltage probe, canbe exercised anywhere within the electrical (RF) circuit, such as withina RF transmission line. Furthermore, the measurement of an electricalsignal, such as a time trace of voltage or current, permits thetransformation of the signal into frequency space using discrete Fourierseries representation (assuming a periodic signal). Thereafter, theFourier spectrum (or for a time varying signal, the frequency spectrum)can be monitored and analyzed to characterize the state of plasmaprocessing system 1. An endpoint signal can be ascertained from avoltage signal, a current signal, an impedance signal, or a harmonicsignal thereof. A voltage-current probe can be, for example, a device asdescribed in detail in pending U.S. application Ser. No. 60/259,862filed on Jan. 8, 2001, or in U.S. Pat. No. 5,467,013 issued to Sematech,Inc. on Nov. 14, 1995; each of which is incorporated herein by referencein its entirety.

In alternate embodiments, diagnostic system 12 can comprise a broadbandRF antenna useful for measuring a radiated RF field external to plasmaprocessing system 1. An endpoint signal can be ascertained from aradiated signal, or a harmonic signal thereof. A commercially availablebroadband RF antenna is a broadband antenna such as Antenna ResearchModel RAM-220 (0.1 MHz to 300 MHz). The use of a broadband RF antenna isdescribed in greater detail in pending U.S. application No. 60/393,101filed on Jul. 3, 2002, pending U.S. application No. 60/393,103 filed onJul. 3, 2002, and pending U.S. application No. 60/393,105 filed on Jul.3, 2002; each of which is incorporated herein by reference in theirentirety.

In alternate embodiments, an endpoint signal can be ascertained from adiagnostic system 12 coupled to an impedance match network to monitorcapacitor settings in the impedance match network. The impedance matchnetwork can be, for example, impedance match network 50 in FIGS. 2through 5, impedance match network 74 in FIG. 4, and impedance matchnetwork 84 in FIG. 5.

In the illustrated embodiment, shown in FIG. 3, the plasma processingsystem 1 can, for example, further comprise either a stationary, ormechanically or electrically rotating DC magnetic field system 60, inorder to potentially increase plasma density and/or improve plasmaprocessing uniformity, in addition to those components described withreference to FIGS. 1 and 2. Moreover, controller 14 is coupled torotating magnetic field system 60 in order to regulate the speed ofrotation and field strength. The design and implementation of a rotatingmagnetic field is well known to those skilled in the art.

In the illustrated embodiment, shown in FIG. 4, the plasma processingsystem 1 of FIGS. 1 and 2 can, for example, further comprise an upperelectrode 70 to which RF power can be coupled from RF generator 72through impedance match network 74. A typical frequency for theapplication of RF power to the upper electrode can range from 10 MHz to200 MHz and is preferably 60 MHz. Additionally, a typical frequency forthe application of power to the lower electrode can range from 0.1 MHzto 30 MHz and is preferably 2 MHz. Moreover, controller 14 is coupled toRF generator 72 and impedance match network 74 in order to control theapplication of RF power to upper electrode 70. The design andimplementation of an upper electrode is well known to those skilled inthe art.

In the illustrated embodiment, shown in FIG. 5, the plasma processingsystem of FIG. 1 can, for example, further comprise an inductive coil 80to which RF power is coupled via RF generator 82 through impedance matchnetwork 84. RF power is inductively coupled from inductive coil 80through dielectric window (not shown) to plasma processing region 45. Atypical frequency for the application of RF power to the inductive coil80 can range from 10 MHz to 100 MHz and is preferably 13.56 MHz.Similarly, a typical frequency for the application of power to the chuckelectrode can range from 0.1 MHz to 30 MHz and is preferably 13.56 MHz.In addition, a slotted Faraday shield (not shown) can be employed toreduce capacitive coupling between the inductive coil 80 and plasma.Moreover, controller 14 is coupled to RF generator 82 and impedancematch network 84 in order to control the application of power toinductive coil 80. In an alternate embodiment, inductive coil 80 can bea “spiral” coil or “pancake” coil in communication with the plasmaprocessing region 15 from above as in a transformer coupled plasma (TCP)reactor. The design and implementation of an inductively coupled plasma(ICP) source, or transformer coupled plasma (TCP) source, is well knownto those skilled in the art.

Alternately, the plasma can be formed using electron cyclotron resonance(ECR). In yet another embodiment, the plasma is formed from thelaunching of a Helicon wave. In yet another embodiment, the plasma isformed from a propagating surface wave. Each plasma source describedabove is well known to those skilled in the art.

In the following discussion, an in-situ method of determining an etchrate and an etch rate uniformity for etching a layer on a substrate inplasma processing system 1 is presented using optical emissionspectroscopy (OES) as an example. However, the methods discussed are notto be limited in scope by this exemplary presentation.

Referring again to FIGS. 1 through 5, diagnostic system 12 can comprisean optical diagnostic subsystem that is utilized to measure theirradiance, or spectral irradiance, of light emitted from the plasma.For example, FIG. 6 presents an exemplary endpoint signal 100 for lightof a given wavelength emitted from plasma in the process space 15 andits first derivative 118. The endpoint signal 100 can further comprisean endpoint transition 110, wherein a distinct change in endpoint signal100 constitutes an endpoint of the process. For example, light emissioncorresponding to a specific chemical constituent present during the etchreaction, that either decays (as in FIG. 6) or increases inconcentration (and, hence, spectral irradiance) during endpoint, can beselected for monitoring purposes.

In an embodiment of the present invention, an etch rate for a layer ofmaterial comprising a thickness T can be determined from a ratio of thethickness T to the time duration between the start of the etch process(i.e. time t₀=0 in the signal endpoint 100) and a time t during theendpoint transition 110. In this case, $\begin{matrix}{{E \cong \frac{T}{( {t - t_{0}} )}},} & (1)\end{matrix}$where E is the etch rate.

In another embodiment of the present invention, an etch rate for a layerof material comprising a minimum thickness T_(min), a maximum thicknessT_(max), and a mean thickness T_(mean) can be determined from the ratioof the minimum layer thickness to the time duration beginning with thestart of the etch process (i.e. time t₀=0 in the endpoint signal 100) tothe start time 112 of the endpoint transition 110 (see FIG. 6). In thiscase, $\begin{matrix}{{E \cong \frac{T_{\min}}{( {t_{112} - t_{0}} )}},} & (2)\end{matrix}$where E is the etch rate, t₀ is the starting time of the etch process,and t₁₁₂ is the starting time 112 of the endpoint transition 110.

In another embodiment of the present invention, an etch rate for a layerof material comprising a minimum thickness T_(min), a maximum thicknessT_(max), and a mean thickness T_(mean) can be determined from the ratioof the maximum layer thickness to the time duration beginning with thestart of the etch process (i.e. time t₀=0 in the endpoint signal 100) tothe end time 114 of the endpoint transition 110 (see FIG. 6). In thiscase, $\begin{matrix}{{E \cong \frac{T_{\max}}{( {t_{114} - t_{0}} )}},} & (3)\end{matrix}$where E is the etch rate, t₀ is the starting time of the etch process,and t₁₁₄ is the end time 114 of the endpoint signal 110.

In another embodiment of the present invention, an etch rate for a layerof material comprising a minimum thickness T_(min), a maximum thicknessT_(max), and a mean thickness T_(mean) can be determined from the ratioof the mean layer thickness to the time duration beginning with thestart of the etch process (i.e. time t₀=0 in the endpoint signal 100) tothe inflection time 116 of the endpoint transition 110 corresponding tothe inflection point in endpoint transition 110 or the maximum (innegative slope) of the first derivative 118 of the endpoint signal 100(see FIG. 6). In this case, $\begin{matrix}{{E \cong \frac{T_{mean}}{( {t_{116} - t_{0}} )}},} & (4)\end{matrix}$where E is the etch rate, t₀ is the starting time of the etch process,and t₁₁₆ is the inflection time 116 of the endpoint transition 110 asdescribed above.

In another embodiment of the present invention, an etch rate uniformityfor a layer of material comprising a minimum thickness T_(min), amaximum thickness T_(max), a mean thickness T_(mean), and a thicknessrange ΔT can be determined from the maximum etch rate E_(max), theminimum etch rate E_(min), the maximum thickness, the thickness range,and the time span Δt (indicated as 120 in FIG. 6) of the endpointtransition 110. In this case, $\begin{matrix}{{{\Delta\quad E} \cong {\frac{E_{\max}E_{\min}}{T_{\max}}( {{\Delta\quad t} - \frac{\Delta\quad T}{E_{\max}}} )}},} & (5)\end{matrix}$where ΔE is the etch rate uniformity. Since EmaxEmin˜E2, equation (5)can be simplified as $\begin{matrix}{{\Delta\quad E} \cong {\frac{E}{T_{\max}}{( {{E\quad\Delta\quad t} - {\Delta\quad T}} ).}}} & (6)\end{matrix}$

In another embodiment of the present invention, an etch rate for a layerof material comprising a minimum thickness T_(min), a maximum thicknessT_(max), and a mean thickness T_(mean) can be determined from two ormore signals from diagnostic system 12, such as endpoint signals 100Aand 100B shown in FIGS. 7A and 7B. Endpoint signal 100A can, forexample, correspond to emission from a chemical constituent whoseconcentration decays during endpoint, and endpoint signal 100B can, forexample, correspond to emission from a chemical constituent whoseconcentration rises during endpoint. One or more ratio signals can thenbe determined from the two or more signals, such as the ratio signal 130(FIG. 7C) determined by dividing endpoint signal 100A by endpoint signal100B at each instant in time. Furthermore, one or more differentialsignals can be determined from the one or more ratio signals, such asdifferential signal 140 (FIG. 7D) determined from a first derivative ofthe ratio signal 130. For example, the first derivative can be estimatedusing a first order (forward or backward) difference scheme, or a secondorder (central) difference scheme. As described above, an etch rate canbe determined from the ratio of the mean layer thickness to the timeduration beginning with the start of the etch process (i.e. time t=0 inthe signals 100A, 100B) to the inflection time of the ratio signal 130corresponding to the inflection point in ratio signal 130 (FIG. 7C) orthe maximum 142 (in negative slope) of the differential signal 140 (seeFIG. 7D). In this case, $\begin{matrix}{{E \cong \frac{T_{mean}}{( {t_{142} - t_{0}} )}},} & (7)\end{matrix}$where E is the etch rate, t₀ is the starting time of the etch process,and t₁₄₂ is the time corresponding to the negative slope maximum 142 indifferential signal 140. Moreover, an etch rate uniformity can bedetermined from equation (6) as described above.

As described above, the endpoint signal, as depicted in FIG. 6, cancomprise a raw (unfiltered) endpoint signal. Alternately, in some caseswhere the signal-to-noise ratio can be low, filtering the endpointsignal can be necessary to smooth the raw signal. In such cases, signalfiltering can comprise at least one of applying moving (running)averages, and finite impulse response functions to the raw signal. Forexample, FIGS. 8A and 8B present typical raw endpoint signals 101A,101B, and corresponding smoothed endpoint signals 150A, 150B using amoving average. Alternately, when derivatives are taken of an endpointsignal or ratio signal, additional filtering can be imposed eitherexplicitly or implicitly. For example, signal differencing can beperformed using one of simple differencing schemes as described above,simple differencing and smoothing (i.e. moving average of the differencesignal), and a Savitsky-Golay filter. In the latter, further details areprovided in co-pending U.S. Application Ser. No. 60/______, entitled“Method and apparatus for detecting endpoint”, Attorney docket No.228160USUS6YA PROV, filed on even date herewith, which is incorporatedherein by reference in its entirety.

FIG. 9 presents an in-situ method of determining an etch property foretching a layer on a substrate in a plasma processing system accordingto an embodiment of the present invention. The method is illustrated ina flowchart 200 beginning in step 210 with providing a thickness of thelayer etched on the substrate in the plasma processing system described,for example, in FIGS. 1 through 5. The thickness can, for example,comprise at least one of a minimum thickness, a maximum thickness, amean thickness, and a thickness range. Prior to etching the layer, oneor more layer thicknesses are generally known. In step 220, the layer isetched utilizing processes known to those skilled in the art of dryetching with plasma and beginning at an etch start time.

In step 230, at least one endpoint signal is measured using a diagnosticsystem coupled to a process chamber, wherein the process chamber isutilized to facilitate the process prescribed for the plasma processingsystem. The diagnostic system can comprise at least one of an opticaldiagnostic subsystem and an electrical diagnostic subsystem. Forexample, the optical diagnostic subsystem can comprise at least one of adetector, an optical filter, a grating, a prism, a monochromator, and aspectrometer. Additionally, for example, the electrical diagnosticsubsystem can comprise at least one of a voltage probe, a current probe,a spectrum analyzer, an external RF antenna, a power meter, and acapacitor setting monitor. The at least one endpoint signal can comprisean endpoint transition as described above. Furthermore, the endpointtransition can comprise a starting time, an end time, and an inflectiontime. Additionally, for example, the at least one endpoint signal cancomprise a spectral irradiance of light emitted from the plasma.

In step 240, an etch rate for the etching of the layer on the substratein the plasma processing system is determined using the at least oneendpoint signal and the thickness of the layer. For example, the etchrate can be determined from a ratio of the minimum thickness of thelayer to the difference in time between the starting time of theendpoint transition and the starting time of the layer etching (seeequation (2)). Alternately, the etch rate can be determined from a ratioof the maximum thickness of the layer to the difference in time betweenthe end time of the endpoint transition and the starting time of thelayer etching (see equation (3)). Alternately, the etch rate can bedetermined from a ratio of the mean thickness of the layer to thedifference in time between the inflection time of the endpointtransition and the starting time of the layer etching (see equation(4)). Alternately, the at least one endpoint signal can comprise twoendpoint signals, namely, a first endpoint signal and a second endpointsignal. A ratio signal can be determined from the first and secondendpoint signal by performing a ratio of the two signals at each instantin time. The ratio signal can further comprise an endpoint transition,wherein the endpoint transition comprises a starting time, an end time,and an inflection time. Furthermore, the etch rate can be determinedfrom the ratio signal using any one of the above described methods inequations (2) through (4), or (7).

The in-situ method described in flowchart 200 can further comprise step250 wherein a time duration of the endpoint transition is determined.For example, the time duration of the endpoint transition can bedetermined from the first derivative of an endpoint signal as indicatedby 120 in FIG. 6, or from the first derivative of the ratio signal oftwo endpoint signals as indicated by 144 in FIG. 7D.

In step 260, an etch rate uniformity is determined from the etch ratedetermined in step 240, the time duration of the endpoint transitiondetermined in step 250, and the thickness range of the layer etched. Forexample, the etch rate uniformity can be determined utilizing equation(6).

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A plasma processing system for etching a layer on a substratecomprising: a process chamber; a diagnostic system coupled to saidprocess chamber and configured to measure at least one endpoint signal;and a controller coupled to said diagnostic system and configured todetermine at least one of an etch rate and an etch rate uniformity of anetching process in said processing chamber from said at least oneendpoint signal and a thickness of said layer, wherein said thicknesscomprises at least one of a minimum thickness, a maximum thickness, amean thickness, and a thickness range.
 2. The plasma processing systemas recited in claim 1, wherein said diagnostic system comprises at leastone of an optical diagnostic subsystem and an electrical diagnosticsubsystem.
 3. The plasma processing system as recited in claim 2,wherein said optical diagnostic subsystem comprises at least one of adetector, an optical filter, a grating, and a prism.
 4. The plasmaprocessing system as recited in claim 2, wherein said optical diagnosticsubsystem comprises at least one of a spectrometer and a monochromator.5. The plasma processing system as recited in claim 2, wherein saidelectrical diagnostic subsystem comprises at least one of a voltageprobe, a current probe, a spectrum analyzer, an external RF antenna, apower meter, and a capacitor setting monitor.
 6. The plasma processingsystem as recited in claim 1, wherein said at least one endpoint signalcomprises an endpoint transition.
 7. The plasma processing system asrecited in claim 6, wherein said endpoint transition comprises astarting time, an end time, and an inflection time.
 8. The plasmaprocessing system as recited in claim 7, wherein said etch rate isdetermined from a ratio of said minimum thickness of said layer to saidstarting time of said endpoint transition.
 9. The plasma processingsystem as recited in claim 7, wherein said etch rate is determined froma ratio of said maximum thickness of said layer to said end time of saidendpoint transition.
 10. The plasma processing system as recited inclaim 7, wherein said etch rate is determined from a ratio of said meanthickness of said layer to said inflection time of said endpointtransition.
 11. The plasma processing system as recited in claim 8,wherein said etch rate uniformity ΔE is determined from$E \cong {\frac{E}{T_{\max}}( {{E\quad\Delta\quad t} - {\Delta\quad T}} )}$where T_(max) is said maximum thickness, ΔT is said thickness range, Δtis the time difference between said start time and said end time, and Eis said etch rate.
 12. The plasma processing system as recited in claim1, wherein a ratio signal is determined from a ratio of a first endpointsignal to a second endpoint signal.
 13. The plasma processing system asrecited in claim 12, wherein said ratio signal comprises an endpointtransition.
 14. The plasma processing system as recited in claim 13,wherein said endpoint transition comprises a starting time, an end time,and an inflection time.
 15. The plasma processing system as recited inclaim 14, wherein said etch rate is determined from a ratio of saidminimum thickness of said layer to said starting time of said endpointtransition in said ratio signal.
 16. The plasma processing system asrecited in claim 14, wherein said etch rate is determined from a ratioof said maximum thickness of said layer to said end time of saidendpoint transition in said ratio signal.
 17. The plasma processingsystem as recited in claim 14, wherein said etch rate is determined froma ratio of said mean thickness of said layer to said inflection time ofsaid endpoint transition in said ratio signal.
 18. The plasma processingsystem as recited in claim 1, wherein said at least one endpoint signalis related to a spectral irradiance of emitted light from said plasmaprocessing system.
 19. The plasma processing system as recited in claim1, wherein said at least one endpoint signal is filtered.
 20. An in-situmethod of determining an etch property for etching a layer on asubstrate in a plasma processing system comprising: providing athickness of said layer, wherein said thickness comprises at least oneof a minimum thickness, a maximum thickness, a mean thickness, and athickness range; etching said layer on said substrate; measuring atleast one endpoint signal using a diagnostic system coupled to saidplasma processing system, wherein said at least one endpoint signalcomprises an endpoint transition; and determining said etch rate from aratio of said thickness to a difference between a time during saidendpoint transition and a starting time of said etching.
 21. The methodas recited in claim 20, wherein said diagnostic system comprises atleast one of an optical diagnostic subsystem and an electricaldiagnostic subsystem.
 22. The method as recited in claim 21, whereinsaid optical diagnostic subsystem comprises at least one of a detector,an optical filter, a grating, and a prism.
 23. The method as recited inclaim 21, wherein said optical diagnostic subsystem comprises at leastone of a spectrometer and a monochromator.
 24. The method as recited inclaim 21, wherein said electrical diagnostic subsystem comprises atleast one of a voltage probe, a current probe, an external RF antenna, apower meter, a spectrum analyzer, and a capacitor setting monitor. 25.The method as recited in claim 20, wherein said endpoint transitioncomprises a starting time, an end time, and an inflection time.
 26. Themethod as recited in claim 25, wherein said thickness is said minimumthickness of said layer and said time is said starting time of saidendpoint transition.
 27. The method as recited in claim 25, wherein saidetch rate is determined from a ratio of said maximum thickness of saidlayer to said end time of said endpoint transition in one of said atleast one endpoint signals.
 28. The method as recited in claim 25,wherein said etch rate is determined from a ratio of said mean thicknessof said layer to said inflection time of said endpoint transition in oneof said at least one endpoint signals.
 29. The method as recited inclaim 20, wherein said at least one endpoint signal comprises twoendpoint signals.
 30. The method as recited in claim 29, wherein a ratiosignal is determined from a ratio of a first endpoint signal of said twoendpoint signals to a second endpoint signal of said two endpointsignals.
 31. The method as recited in claim 30, wherein said ratiosignal comprises an endpoint transition.
 32. The method as recited inclaim 31, wherein said endpoint transition comprises a starting time, anend time, and an inflection time.
 33. The method as recited in claim 32,wherein said etch rate is determined from a ratio of said minimumthickness of said layer to said starting time of said endpointtransition in said ratio signal.
 34. The method as recited in claim 32,wherein said etch rate is determined from a ratio of said maximumthickness of said layer to said end time of said endpoint transition insaid ratio signal.
 35. The method as recited in claim 32, wherein saidetch rate is determined from a ratio of said mean thickness of saidlayer to said inflection time of said endpoint transition in said ratiosignal.
 36. The method as recited in claim 20, wherein said at least oneendpoint signal is related to a spectral irradiance of emitted lightfrom said plasma processing system.
 37. The method as recited in claim20, wherein said at least one endpoint signal is filtered.
 38. Themethod as recited in claim 20, wherein said method further comprisesdetermining a time duration for said endpoint transition of said atleast one endpoint signal.
 39. The method as recited in claim 38,wherein said method further comprises determining an etch rateuniformity from said etch rate, said time duration of said endpointtransition, and said thickness range of said layer.
 40. The method asrecited in claim 31, wherein said method further comprises determining atime duration for said endpoint transition of said ratio signal.
 41. Themethod as recited in claim 40, wherein said method further comprisesdetermining an etch rate uniformity from said etch rate; said timeduration of said endpoint transition, and said thickness range of saidlayer.
 42. The plasma processing system as recited in claim 9, whereinsaid etch rate uniformity ΔE is determined from$E \cong {\frac{E}{T_{\max}}( {{E\quad\Delta\quad t} - {\Delta\quad T}} )}$where T_(max) is said maximum thickness, ΔT is said thickness range, Δtis the time difference between said start time and said end time, and Eis said etch rate.
 43. The plasma processing system as recited in claim10, wherein said etch rate uniformity ΔE is determined from$E \cong {\frac{E}{T_{\max}}( {{E\quad\Delta\quad t} - {\Delta\quad T}} )}$where T_(max) is said maximum thickness, ΔT is said thickness range, Δtis the time difference between said start time and said end time, and Eis said etch rate.